New 4th axis

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Re: New 4th axis

Postby ger21 » Wed Mar 20, 2019 11:39 am

Use G93. You can convert your standard code with this:

https://www.ganotechnologies.com/cnc/rapidrotary/

I was playing with it over the weekend, and it worked well.
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Re: New 4th axis

Postby Battwell » Wed Mar 20, 2019 1:32 pm

Great find ger!
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Re: New 4th axis

Postby ger21 » Wed Mar 20, 2019 2:06 pm

Thank Greg. He pointed this out months ago, when he was asking for G93 support.
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Re: New 4th axis

Postby spumco » Wed Mar 20, 2019 8:53 pm

I knew I remembered something like that.

I've GOT to give it a go soon.
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Re: New 4th axis

Postby ThreeDJ16 » Thu Mar 21, 2019 12:10 am

So let's say I used a timing belt driven 4th axis and servo, you couldn't modify the Fusion 360 post to do the same thing? Or is Fusion 360 still just 3 + 1 axis, as I thought they'd upgraded last year or so to true 4th axis?
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Re: New 4th axis

Postby spumco » Sun Mar 24, 2019 5:05 am

No, F360 is full 4th continuous.

As long as your 4th axis is fast enough to keep up with the x/y at the desired feed rate I don't think it matters whether it's a belt, worm, harmonic, cycloidal, or some combo.

In the video Gerry linked, first example, shows that his CAM was moving all the axis, including the rotary, at the same feedrate. Instead of 80IPM at the surface, he was getting 80 degrees/minute. Too slow.

I think that the new rotary axis feature in UCCNC does what the video Gerry posted accomplishes. UCCNC - and someone please correct me if I'm wrong - disregards the 4th axis when it calculates the X/Y/Z feedrate, but it still slows down the X/Y/Z feed so that you still get the desired tool path and everything moves as fast as possible -only restricted by the upper speed of the rotary axis. And without the G93 command.

The current UCCNC PP doesn't use G93/G94, but I'm sure you could modify it. Next time in in F360 I'll model up a quick continuous 4th toolpath and see what it puts out. I suspect it'll output the feedrate the same as in the video - in Fxx units. All of my 4th axis stuff so far has just been indexing, so all I've seen is G0 commands.

I'm curious to see how UCCNC will handle 4th axis moves where the X//Z feedrates are lower than the maximum A-axis speed. How does UCCNC know how fast to turn the rotary axis in relation to the A?
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Re: New 4th axis

Postby cncdrive » Sun Mar 24, 2019 5:11 am

Yes, correct, the rotary axis feature pulls the ABC axis (optionally) out of the path feedrate calculation and so then for example if the A axis is set to rotary and there is e.g. a move XYA then the programmed feedrate is calculated on the XY axes only, the A axis is just following, in other words the feedrate is calculated on the XY path and the A axis finishes the move the same time when the XY finishes with the calculated feedrate (speed).
So, yes, the G93 is good exactly for what is shown on that video.
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Re: New 4th axis

Postby ger21 » Sun Mar 24, 2019 12:50 pm

No, F360 is full 4th continuous


Since when? Or are you referring to the wrapped toolpaths?

I can't find anything that shows continuous 4th axis.
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Re: New 4th axis

Postby spumco » Mon Mar 25, 2019 12:37 am

Gerry/All

I guess I wasn't terribly precise. F360 can't do continuous 4th axis with Z-moves (conical or cam shaped features). It can do 'continuous' rotary axis via Wrap - as you mentioned - but not I guess what most people think of as Continuous 3D 4th axis stuff.

Reading the F360 forums, some people have had limited success using the Flow toopath to generate continuous 4th axis toolpaths.

Sorry if anyone got excited...

-R
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Re: New 4th axis

Postby ger21 » Mon Mar 25, 2019 1:13 am

I watched a video today that claimed to be 4 axis flow, but appeared to really be 4 axis.
I tried something similar, and couldn't get it to work. Seems to be pretty fussy about axis directions.
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